The present invention relates to a propylene resin composition and a method for producing it. Precisely, the invention relates to a propylene resin composition comprising specific two different types of propylene polymers; apropylene resin composition comprising the composition, an elastomer and an inorganic filler; and a method for producing the compositions.
High-grade polypropylene with high stiffness, high impact strength and high fluidity is desired in the field of automobile parts, parts of electric and electronic appliances for household use, parts of housing facilities, and others relating to them. To meet the need of such high-grade polypropylene, known is a method of producing a resin composition by blending at least two different types of propylene resins having different characteristics. However, the resin composition produced could be hardly uniform, and its impact resistance is low and its appearances are often poor. As a result, the resin composition could hardly have well-balanced physical properties.
On the other hand, proposed are propylene-ethylene block copolymers to be produced in a continuous polymerization device (Japanese Patent Laid-Open No. 194685/1993). However, their moldings often have defective appearanceswithfisheyes, and it is difficult to obtain copolymer moldings with good appearances according to the proposed technique. To prevent or reduce fish eyes, proposed is a method of imparting high shear stress to a mass of resin (Japanese Patent Laid-Open Nos. 339920/1994 and 176230/1997). However, the method is unfavorable, as the resin processed therein is degraded and its physical properties are worsened.
The present invention is to provide a propylene resin composition having high stiffness, high impact strength, high fluidity and good appearances, and to provide a method for producing it.
I, the present inventor has assiduously studied the problems noted above, and, as a result, has found the following: Of propylene resin compositions prepared by mixing at least two different types of propylene polymers in melt, those in which the viscosity difference between the propylene homopolymer segments to form the continuous phase and the amorphous segments (more strictly, ethylene-propylene copolymer segments) to form the disperse phase is smaller have a fewer fish eyes when molded; and for those in which the viscosity difference therebetween is large, effective is a method of separately melting and kneading the constituent propylene polymers followed by further kneading the resulting plural melts so as to prevent them from having fish eyes when molded. On the basis of these findings, the inventor has completed the present invention, which is summarized as follows:
[1] A propylene resin composition (A) comprising the following components (A-1) and (A-2):
(A-1) from 60 to 80% by mass of a propylene homopolymer and/or a propylene-ethylene block copolymer having the following properties (a1) to (a5):
(a1) The amount of its xylene-insoluble ingredient falls between 90 and 100% by mass;
(a2) Its ingredient insoluble both in xylene and in boiling n-heptane has a stereospecificity index of at least 96.5%;
(a3) Its ingredient insoluble both in xylene and in boiling n-heptane has an intrinsic viscosity [xcex7T]1-c falling between 0.6 and 1.1 dl/g;
(a4) When this contains a propylene-ethylene block copolymer, the ethylene content of its xylene-soluble ingredient falls between 15 and 45% by mass;
(a5) When this contains a propylene-ethylene block copolymer, the intrinsic viscosity [xcex7T]1-A of its xylene-soluble ingredient falls between 2.5 and 5.0 dl/g with [xcex7]1-A/[xcex7]1-C less than 6.5;
(A-2) from 20 to 40% by mass of a propylene-ethylene block copolymer having the following properties (axe2x80x21) to (axe2x80x25):
(axe2x80x21) The amount of its xylene-insoluble ingredient falls between 70 and 90 parts by mass;
(axe2x80x22) Its ingredient insoluble both in xylene and in boiling n-heptane has a stereospecificity index of at least 96.5%;
(axe2x80x23) Its ingredient insoluble both in xylene and in boiling n-heptane has an intrinsic viscosity [xcex7]2-C falling between 1.1 and 1.8 dl/g;
(axe2x80x24) The ethylene content of its xylene-soluble ingredient falls between 15 and 45% by mass;
(axe2x80x25) The intrinsic viscosity [xcex7]2-A of its xylene-soluble ingredient falls between 6.0 and 10.0 dl/g with 4.0 less than [xcex7]2-A/[xcex7]2-C less than 6.5.
[2] The propylene resin composition of above [1], wherein the component (A-1) is a propylene homopolymer or a propylene/ethylene block copolymer, and [xcex7]1-A/[xcex7]1-C less than 4.0 when it contains a propylene-ethylene block copolymer.
[3] The propylene resin composition of above [1], wherein the component (A-1) contains a propylene/ethylene block copolymer, and 4.0xe2x89xa6[xcex7]1-A/[xcex7]1-C less than 6.5.
[4] The propylene resin composition of anyof above [1] to [3], which is prepared by simultaneously kneading both the component (A-1) and the component (A-2) all in melt by the use of a unidirectional rotary double-screw extruder with L/D falling between 20 and 60.
[5] The propylene resin composition of above [2], which is prepared by first kneading the component (A-2) in melt by the use of a unidirectional rotary double-screw extruder with L/D falling between 20 and 60, followed by adding the component (A-1) thereto and further kneading the resulting mixture in melt.
[6] Thepropylene resin composition of above [5], which is prepared by top-feeding the component (A-2) with side-feeding the component (A-1).
[7] Thepropylene resin compositionof above [3], which is prepared by separately melting, kneading and granulating the components (A-1) and (A-2) by the use of a unidirectional rotary double-screw extruder with L/D falling between 20 and 60, followed by combining the resulting granules and further kneading them in melt.
[8] A propylene resin composition comprising (A) 100 parts by mass of the propylene resin composition of any of above [1] to [7], (B) at most 50 parts by mass (excluding 0) of an elastomer mentioned below, and/or (C) at most 50 parts by mass (excluding 0) of an inorganic filler:
(B) An elastomer comprising the following component (B-1) and/or component (B-2):
(B-1) An ethylene-xcex1-olefin elastomer having the following properties (b1) and (b2):
(b1) Its xcex1-olefin content falls between 10 and 40 mol %;
(b2) Its intrinsic viscosity [xcex7] falls between 0.9 and 2.5 dl/g;
(B-2) A styrene elastomer having the following properties (bxe2x80x21) and (bxe2x80x22):
(bxe2x80x21) Its styrene content falls between 12 and 50% by mass;
(bxe2x80x22) Its intrinsic viscosity [xcex7] falls between 0.1 and 2.0 dl/g.
[9] A method for producing a propylene resin composition, whichcomprisesmeltingandkneading (A) 100parts by mass of the propylene resin composition of any of above [1] to [7], (B) at most50parts by mass (excluding 0) of an elastomer mentioned below, and/or (C) at most 50 parts by mass (excluding 0) of an inorganic filler, by the use of a unidirectional rotary double-screw extruder with L/D falling between 20 and 60, or a tandem kneader:
(B) An elastomer comprising the following component (B-1) and/or component (B-2):
(B-1) An ethylene-xcex1-olefin elastomer having the following properties (b1) and (b2):
(b1) Its xcex1-olefin content falls between 10 and 40 mol %;
(b2) Its intrinsic viscosity [xcex7] falls between 0.9 and 2.5 dl/g;
(B-2) A styrene elastomer having the following properties (bxe2x80x21) and (bxe2x80x22)
(bxe2x80x21) Its styrene content falls between 12 and 50% by mass;
(bxe2x80x22) Its intrinsic viscosity [xcex7] falls between 0.1 and 2.0 dl/g.
[10] A method for producing a propylene resin composition, which comprises melting and kneading a mixture prepared by melting, kneading and granulating the component (A-2) by the use of a unidirectional rotary double-screw extruder with L/D falling between 20 and 60, followed by adding thereto the component (A-1) of a propylene homopolymer or a propylene-ethylene block copolymer with [xcex7]1-A/[xcex7]1-C less than 4.0 when it contains a propylene-ethylene block copolymer, to reach 100 parts by mass in total of the component (A-1) and the component (A-2); at most 50 parts by mass (excluding 0), relative to 100 parts by mass of the total of the components (A-1) and (A-2), of an elastomer of the following component (B), and/or at most 50 parts by mass (excluding 0), relative to 100 parts by mass of the total of the components (A-1) and (A-2), of an inorganic filler (C), by the use of a tandem kneader:
(B) An elastomer comprising the following component (B-1) and/or component (B-2):
(B-1) An ethylene-xcex1-olefin elastomer having the following properties (b1) and (b2):
(b1) Its xcex1-olefin content falls between 10 and 40 mol %;
(b2) Its intrinsic viscosity [xcex7] falls between 0.9 and 2.5 dl/g;
(B-2) A styrene elastomer having the following properties (bxe2x80x21) and (bxe2x80x22):
(bxe2x80x21) Its styrene content falls between 12 and 50% by mass;
(bxe2x80x22) Its intrinsic viscosity [xcex7] falls between 0.1 and 2.0 dl/g.
[11] The method for producing a propylene resin composition of above [9] or [10], wherein the tandem kneader comprises a bi-directional rotary double-screw kneader unit (with vent (s) and with L/D falling between 3 and 20) combined with a single-screw extruder (with vent(s) and with L/D falling between 5 and 60) or with a double-screw extruder (with vent(s) and with L/D falling between 5 and 60).
[12] A propylene resin composition obtained according to the production method of any of above [9] and [11].